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Applications in Water Harvesting Systems

Applications in Water Harvesting Systems

Water harvesting in commercial projects ...

Safety Relief Valve FAQs

Safety Relief Valve FAQs

Companies that repair, test, maintain or...

An Update on U.S. Valve-Related Standards

An Update on U.S. Valve-Related Standards

It takes much time and effort by many pe...

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Industry Headlines

Leading Economic Indicators for the U.S. Increased in July

Wednesday, 23 August 2017  |  Chris Guy

The Conference Board Leading Economic Index (LEI) for the U.S. increased 0.3% in July to 128.3 (2010 = 100), following a 0.6% increase in June, and a ...

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Low Cracking Pressure in Chemical Processing Condensate Lines

Low Cracking Pressure in Chemical Processing Condensate Lines

Tuesday, 22 August 2017  |  Arie Bregman

Steam condensate is the liquid by-product formed when steam goes from the vapor state to the liquid state; this process occurs in a wide range of appl...

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Industry Headlines

Velan Names Duc Tran Vice-President, Engineering

14 HOURS AGO

Velan Inc. has appointed Duc Tran as its new vice-president, engineering. Tran will be a key member of the company's senior management team and is succeeding Gil Perez, who has assumed a new mandate as vice-president, product technology and strategic initiatives. He will report directly to president...

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AIV and Gulf Coast Modification Opening NW Houston Facility

1 DAY AGO

AIV, LP has announced plans for a new 320,000+ square-foot facility at NW Lake Drive, near Telge Road and Highway 290 in northwest Houston. The 32-acre construction site allows for the future expansion of up to 700,000 sq. ft. This facility will consolidate AIV and Gulf Coast Modification ’s curr...

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Group Asking Feds to Halt LNG Exports

12 HOURS AGO

The Industrial Energy Consumers of America recently sent a letter to the Secretary of Energy on two LNG export demand scenarios. They argue that the Obama Administration’s “public interest” LNG export studies, which are still being used to justify LNG export approvals to non-free tra...

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Chemical Activity Barometer Shows Modest Slowing

1 DAY AGO

The Chemical Activity Barometer (CAB) from the American Chemistry Council remained unchanged from July, continuing a modest deceleration of growth. The flat reading follows a 0.1% increase in July and a flat reading in June. Compared to a year earlier, the CAB is up 3.2% year-over-year, an easing fr...

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Leading Economic Indicators for the U.S. Increased in July

9 HOURS AGO

The Conference Board Leading Economic Index (LEI) for the U.S. increased 0.3% in July to 128.3 (2010 = 100), following a 0.6% increase in June, and a 0.3% increase in May.

“The U.S. LEI improved in July, suggesting the U.S. economy may experience further improvements in economic activity in the...

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U.S. Factory Output Declined in July

5 DAYS AGO

Manufacturing output edged down 0.1% in July. The index for durables decreased 0.5%. Among durable manufacturing industries, with the indexes for primary metals and for furniture and related products each dropped more than 1%. The index for other manufacturing (publishing and logging) moved down 0.4%....

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A Case for Mechanical Temperature Control

vmwnt12_beyond_valves_fig1Instrument, mechanical or project engineers may see a multitude of temperature applications cross their desks. Their immediate reaction might be to employ a temperature control loop. But could a mechanical, self-operated temperature regulator be a better solution for the valve application?

When approaching a temperature control application, the engineer usually considers:

  • The degree of accuracy needed
  • Whether the application requires feedback (Are limit switches/output signals used?)
  • Whether the application needs to be controlled through a DCS, PLC or other type of controller
  • The budget for the application.

The answer to whether a mechanical temperature regulator might be a cost-effective and reliable solution for the application depends on those considerations.

In almost any process facility, a variety of temperature control applications can be found. As with any controlled variable, both the accuracy and criticality of those applications can vary widely. Often, non-critical temperature applications become instrumented control loops even when a self-operated or mechanical regulator could provide the desired accuracy along with a substantial cost savings.


WHAT’S CONSIDERED

vmwnt12_beyond_valves_fig1Figure 1. Temperature regulatorA typical temperature control loop ­(Figure 1) requires:

  • a temperature sensor
  • wiring and conduit
  • connection to a controlling device
  • a control valve (and sometimes a positioner and/or I/P converter, and an air-filter regulator)
  • plant air

A self-contained temperature regulator requires no power, no air supply or other expensive compo­nents to operate. Representative costs based on a 1-inch line size would be:

  • Temperature transmitter: $300-1,000
  • Temperature controller: $400-1,000
  • Control valve and actuator: $1,500-3,000
  • I/P converter: $200-350
  • Air set regulator: $100-150
  • Positioner: $500-2,000
  • Control loop total: $3,000-7,500
  • Temperature regulator: $500-2,500

Although designs may vary from manufacturer to manufacturer, most temperature regulators operate on the same principle. A premeasured amount of “fill” is drawn into the thermal system filling the upper diaphragm chamber, the capillary tube and most of the bulb. As the controlled temperature increases, the fill in the sensing bulb begins to vaporize and creates pressure on the sealed system. This pressure drives the valve stem, closing direct-acting valves or opening reverse-acting valves. By using different fill fluids, many different temperature control ranges can be offered for both cooling and heating applications—temperature ranges are readily available from -20° F (-29° C) to 500° F (260° C).

Applications for which these devices might be ideal include tank farms, large heat exchangers, heat exchangers with slow temperature changes, area heating/cooling (warehouse/maintenance shops) and steam tracing.

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